Oral and rectal contrast agents for identification of the gastrointestinal tract are needed in NMR imaging. In the search for intraabdominal disease, fluid or feces filled loops of bowel must be distinguished from inflammatory or neoplastic disease, which may also present as mass lesions. In pancreatic imaging, the c-loop of the duodenum must be visualized in order to identify the pancreatic head.
By opacification of the c-loop of the duodenum, the location of the pancreatic head may be determined and differentiated from surrounding soft tissue. In NMR, like CT, soft tissue masses in the abdomen are difficult to distinguish from fluid or feces filled bowel loops. This discrimination could be made with the use of a safe, effective contrast agent. This would enable the diagnosis by NMR imaging of intraabdominal abscesses or neoplastic tissue masses.
Barium sulfate and the iodinated contrast agents used in conventional radiology do not cause a marked change consistently in proton density, T.sub.1 or T.sub.2, in patient examinations necessitating attempts to find new agents. Mineral oil may be used to opacify bowel loops on NMR imaging, increasing the proton density signal. Newhouse et al, Radiology 142: 246 (1982). However, administration of sufficient quantities may be hazardous to the patient. Ferric chloride has been tried experimentally to enhance spin-lattice relaxation (T.sub.1) and allow visualization of the stomach. Young et al, J. Comp. Tomo. 5: 543-546 (1981). Absorption of iron with associated acute symptomatology prevents widespread clinical application of this approach.